Speech Privacy Between Neighboring Workstations in an Open Office - A Laboratory Study

The aim of this study was to show how the basic parameters of an open office affect the speech privacy and speech level between two neighboring workstations. The investigation was carried out in laboratory conditions where two adjacent workstations were located. The parameters studied were screen height, room height, ceiling absorption, floor absorption, screen absorption, and masking sound level. Altogether 50 different combinations were studied at three different masking sound levels and normal voice levels. The horizontal sound field was damped by wall absorbers so that the arrangement resembled a pair of workstations in the middle of a large room. The speech privacy improved with increasing masking sound level, ceiling absorption, screen height, and room height, in the order of partial significance. It was possible to reduce speech levels at most by approximately 15 dBA by using the best combination of ceiling absorber and screen height, compared to the situation without absorbers and screens. However, if the masking sound level was low, below 40 dBA, sufficient speech privacy, i.e. low speech intelligibility, could not be reached. The study emphasizes the importance of masking sound as a basic precondition for good speech privacy if normal voice levels are used in the office. The study also gives preliminary evidence that insufficient attenuation of the horizontal sound field in an open office can seriously undermine the attenuation gained from ceiling absorbers and screens. The acoustical design requires simultaneous solutions for masking sound, and the absorption of horizontal and vertical sound fields.